This invention relates generally to welding chill rings for joining adjacent lengths of metal pipes and, more particularly, is directed to a partially consumable spacer chill ring with pipe alignment and separation means.
It is common practice in the welding industry to employ a chill ring to facilitate the introduction of filler material from a separate source during the first root pass, when welding two pipe ends together. Specifically, the chill ring is constructed of a non-consumable metal ring which is inserted within the pipe ends. Spacer pins are usually employed in conjunction with the chill ring to precisely set the distance between adjacent pipe ends for better control and reliability in the pipe joining operation. However, there is a need to provide a separate source of welding material for the first root pass during the welding operation. Thus, use of such chill rings involves manual welding procedures, which are always subject to human error, due to the wide variance possible in the welder's flow of filler material. Examples of such chill rings can be found in U.S. Pat. Nos. 2,366,579 and 2,764,426.
In order to compensate for the above, totally consumable spacer rings have been used which function to provide the consumable welding material for welding, at least during the first root pass, and which also function to separate and align the pipe ends. Examples of such consumable spacer rings can be found in U.S. Pat. Nos. 1,981,850; 2,792,490; 3,068,827; and 4,335,906, and Swiss Pat. No. 202,285.
The problem with using a totally consumable welding ring, however, is that a gas must be pumped into the interior of the pipes to maintain a positive pressure so as to prevent dripping of the liquified consumable metal within the pipes. Such dripping results in the formation of undesirable icicle-like structures within the pipes. The requirement of adding and maintaining gas within the interior of the pipes makes the welding operation relatively complicated and adds further difficulties, such as removal of the gas and the like. For example, aforementioned U.S. Pat. No. 2,792,490 discloses the use of Argon or other suitable inert gas introduced from a cylinder through a conduit into the interior of the pipes when a totally consumable ring is used.
In order to solve the above problems, the applicant herein has proposed using a combination non-consumable base metal ring surrounded by a consumable filler metal spacer ring, the latter spacing apart the metal pipe ends and providing the welding material for at least the first root pass. Such partially consumable spacer chill rings are described in copending U.S. patent application Ser. Nos. 06/587,492 and 06/241,715, the entire disclosures of which are incorporated herein by reference.
However, with the partially consumable spacer chill ring according to these U.S. patent applications, the consumable ring is relatively narrow. As a result, the pipe ends are extremely close to each other, separated by a small gap having dimensions equal to that of the consumable ring. As a result, during a first root pass of the welding operation, much of the applied heat is drawn away from the weld area by the pipes. With such heat being drawn away, it thereby beomes more difficult to melt the weld material. In addition, there may be an uneven flow of material, resulting in cracking and porosity in the weld.
Other types of welding rings are disclosed in U.S. Pat. Nos. 1,980,530; 2,028,233; 2,206,375; 2,731,933; 3,001,497; 3,002,191; 3,290,772; 3,461,543; 3,639,724; 3,895,924; 4,103,940; and 4,135,739.